For the photoconductive material to constitute an image-forming member for use in solid image pickup device or electrophotography, or to constitute a photoconductive layer for use in image-reading photosensor, it is required to be highly sensitive, to have a high S/N ratio [photocurrent (Ip)/dark current (Id)], to have absorption spectrum characteristics suited for an electromagnetic wave to be irradiated, to be quickly responsive and to have a desired dark resistance. It is also required to be not harmful to living things, especially man, upon the use.
Other than these requirements, it is required to have a property of removing a residual image within a predetermined period of time in solid image pickup device.
Particularly for image-forming members used in an electrophotographic machine which is used as a business machine at the office, causing no pollution is highly important.
From these standpoints, the public attention has been focused on light receiving members comprising amorphous materials containing silicon atoms (hereinafter referred to as "A-Si"), for example, as disclosed in Offenlegungsschriftes Nos. 2,746,967 and 2,855,718 which disclose use of the light receiving member as an image-forming member in electrophotography and in Offenlegungsschrift No. 2,933,411 which discloses use of such light receiving member in an image-reading photosensor.
For the conventional light receiving members comprising a-Si materials, there have been made improvements in their optical, electric and photoconductive characteristics such as dark resistance, photosensitivity, and photoresponsiveness, use-environmental characteristics, economic stability and durability.
However, it is still left to make further improvements in order to make such light receiving member practically usable.
For example, in the case where such conventional light receiving member is used as an image-forming member in electrophotography with the goal of heightening the photosensitivity and dark resistance, there is often observed a residual voltage on conventional light receiving member upon the use, and when it is repeatedly used for a long period of time, fatigue due to the repeated use will be accumulated to cause the so-called ghost phenomena inviting residual images.
Further, in the preparation of the conventional light receiving member using an A-Si material, hydrogen atoms, halogen atoms such as fluorine atoms or chlorine atoms, elements for controlling the electrical conduction type such as boron atoms or phosphorus atoms, or other kinds of atoms for improving the characteristics are selectively incorporated in a light receiving layer of the light receiving member as the layer constituents.
However, the resulting light receiving layer sometimes becomes accompanied with defects on the electrical characteristics, photoconductive characteristics and/or breakdown voltage according to the way of the incorporation of said constituents to be employed.
That is, in the case of using the light receiving member having such light receiving layer, the life of a photocarrier generated in the layer with the irradiation of light is not sufficient, the inhibition of a charge injection from the side of the substrate in a dark layer region is not sufficiently carried out, and image defects likely due to a local breakdown phenomenon (the so-called "white oval marks on half-tone copies") or other image defects due to abrasion upon using a blade for the cleaning (the so-called "white line") are apt to appear on the transferred images on a paper sheet.
Further, in the case where the above light receiving member is used in a humid atmosphere, or in the case where after being placed in that atmosphere it is used, the so-called "image flow" sometimes appears on the transferred images on a paper sheet.
Further in addition, in the case of forming a light receiving layer of a ten and some m.mu. in thickness on an appropriate substrate to obtain a light receiving member, the resulting light receiving layer is likely to invite undesired phenomena such as a thinner space being formed between the bottom face and the surface of the substrate, the layer being removed from the substrate and a crack being generated within the layer following the lapse of time after the light receiving member is taken out from the vacuum deposition chamber.
These phenomena are apt to occur in the case of using a cylindrical substrate to be usually used in the field of electrophotography.
Moreover, there have been proposed various so-called laser printers using a semiconductor laser emitting ray as the light source in accordance with the electrophotographic process. For such laser printer, there is an increased demand to provide an improved light receiving member of having a satisfactorily rapid responsiveness to light in the long wave region in order to enhance its function. In consequence, it is required not only to make a further improvement in an A-Si material itself for use in forming the light receiving layer of the light receiving member but also to establish such a light receiving member which will not invite any of the foregoing problems and to satisfy the foregoing demand.